The provision of score lines in suitable places in containers contributes largely to the consumer-friendliness of a container in that the container can be opened easily without using special tools such as scissors, knives, nails and teeth, the dosability of the contents once the container is opened is considerably improved because an opening of the desired configuration is produced instead of a randomly extending tear; and the aesthetical appearance of the container after it has been opened is improved.
The score lines themselves should comply with the following requirements: the packaging material, after the score line has been provided, may not tear during further treatment, such as filling, transport, storage, the container should continue to comply with predetermined transmission values, i.e. the contents may not lose aroma, smell, taste and the like or there may be no ingress of water vapor, oxygen and the like into the contents through the score lines.
In the method disclosed in GB-A-2,161,427, sheets that are to be folded into a container are provided with score or fold lines by means of a laser beam, with the configuration of the lines corresponding with a mask placeable on the sheet. The sheets are placed one by one underneath the laser beam. Once the score lines have been provided, these sheets are removed. This method is insufficiently efficient for application on an industrial scale and in particular too slow.
The provision of score lines using a laser beam in an advancing web of packaging material is known from U.S. Pat. No. 3,909,582. In that arrangement, the laser beam is stationary and the score line extends in the direction of advance of the web of packaging material. By imparting to the laser source a reciprocating movement transverse to the direction of advance of the web, the score line can acquire an approximately sinusoidal configuration, as described in U.S. Pat. No. 4,549,063.